pentobarbital will reduce the extent or impact of conivaptan by impacting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Check.pentobarbital will decrease the extent or impact of fentanyl intranasal by impacting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Keep track of Carefully. Coadministration of fentanyl with CYP3A4 in